1. Field of the Invention
This invention relates to the field of orthopedic surgery and, in particular, the treatment of fractures by implantation of bone screws for compression and medication.
2. Description of the Prior Art
The use of bone screws for stabilization and fixation of fractures is conventional. The use of lag screws for compression of fractures is also conventional, as shown by McCarthy, U.S. Pat. No. 5,514,138.
Lag screws and anchors with additional holding devices are taught by Bramlet, U.S. Pat. No. 5,849,004 and U.S. Pat. No. 6,443,954. These devices have curved talons which deploy from the interior of a cannulated body to increase the holding power.
Bone pins or screws have been used to access the interior of bones for application of diagnostic and structural components. For example, Kyle, U.S. Pat. No. 4,760,844, teaches the use of a cannulated screw for applying X-ray opaque dye and U.S. Pat. No. 4,653,489 teaches the use of a cannulated lag screw to apply polymethylmethacrylate (PMMA) or bone cement to the interior of a broken bone. In both these devices, the exuded material exits near the distal end of the screw which places the material in the immediate area of the screw threads.
What is lacking in the prior art is a lag screw with devices to increase the holding power of the screw and medicate the afflicted area while maintaining the ability to remove the devices and the screw.